Proteins specific to the nervous system in vertebrates and invertebrates (cephalopods) are being isolated, characterized chemically, and assayed by immunological methods using specific antisera. The proteins are being localized to cell-type and to sets of cells of a given type by immunofluorescence and other methods and are being studied during development of the nervous system. The turnover and extent of axo-plasmic flow of the proteins are being studied. So far two vertebrate proteins, S-100 (glial) and 14-3-2 (neuronal), have been studied intensively and three others, 14-3-3, TC-1, and AG-1 have been purified. One protein, OL-1, has been purified and studied in octopus nervous system.